Having attended and spoken at many conferences myself, I'd like to share some tips to help you have the best experience and get the most out of your next PHP conference.
Before you leave for the conference, figure out which talks you'd like to attend. Are there topics which you need to know for work? Any new technologies you've been wanting to try out? Select a good variety of high-level and in-depth talks. I've found it helpful to print out the list of sessions and circle the ones I'm most interested in.
For multi-track conferences, it's likely that two interesting talks will be given at the same time - if that happens, check whether any similar sessions are going on at a different time and consider attending that. Alternatively, some conferences will record their talks, so you can always watch any you missed at a later date.
Most conferences kick off first thing in the morning. If you're traveling from out-of-town, try to fly in the day before the conference. It'll give you a day to settle in, explore the area, figure out what's around, and get mentally prepared for the next few days. Don't be tempted to save money by arriving day-of; if you're late, tired, or stressed you won't be getting the maximum value out of the conference.
You may be tempted to find cheaper accommodations somewhere else. But if your budget allows, stay at the "official" conference hotel instead. Sometimes this will be the same hotel hosting the conference, otherwise it'll be one close by. By staying there, you'll be closer to the conference venue - you can sleep in a little later and traveling to/from the venue will be easier. Also, most of the speakers and attendees will be staying there too, giving you more opportunities to socialize and network.
Most conferences will have an area for sponsors and exhibitors to show off their products and services. Many will also have free swag like t-shirts, stickers, pens, yo-yos, etc. The good swag is limited and goes quickly (especially medium and large t-shirts), so visit those stands early.
But don't just take the swag and leave - stick around for a minute to learn more. While you may not need their product/service today, it doesn't hurt to learn more about what they offer (in case you do need it one day). So learn what they're about, take some informational material too, and thank them for sponsoring the event.
Conferences aren't just about learning (although that's certainly an important part); they also provide opportunities to network and socialize with others. Some conferences will have evening socials, others might have game nights, etc. Some attendees will even organize their own social outings - dinner at a restaurant, a trip to the nearby casino, karaoke at a local bar, etc. You should absolutely join in, meet new people, and have some fun!
Twitter is the best way to stay connected during the conference. Follow the conference account for updates on schedule changes, event reminders, etc. Each conference will also have a dedicated hashtag you can use to see who else is attending, share pictures, and plan/join social outings.
When I first started attending conferences, I was somewhat starstruck by the speakers - these were big names in the community I looked up to and respected. But I quickly found they're not egotistic celebrities - they're developers just like you and me who want to share their knowledge and meet others. So take the opportunity to chat with them - don't be afraid to ask questions, get advice, pick their brains, or join them at lunch for a casual chat.
Conference organizers rely on feedback to select their speaker lineup. Speakers rely on feedback to improve their talks and presentation skills. So if you really liked a talk, please take the time to let both the organizers and speakers know! Conversely, if a particular talk didn't meet your expectations, leave some constructive feedback so the speaker can improve for future talks they might give. By giving feedback on sites such as joind.in, you are "paying it forward" to help future conference organizers, speakers, and attendees have the best possible conference experience.